Just like Bush in 2004, when, in his second debate with Kerry, there was an odd rectangular hump on the back of his suit jacket, and he would snap "Let me finish!" when Kerry hadn't interrupted him. The Times actually nailed it---in a story they decided not to run.

https://www.thegatewaypundit.com/2020/09/weird-appears-joe-bidens-wire-slipped-jacket-presidential-debate/